Connection of a microprocessor to a peripheral circuit is a common requirement. Because mircroprocessors utilize various read and write timing signals at the interface to the peripheral circuit, customized interface circuitry has been required. A typical arrangement are microprocessors manufactured by the Intel Corporation which use a read strobe and a wirte strobe, while those manufactured by the Motorola Corporation use a data strobe and a read/write indicator.
Peripheral devices are therefore directly compatible with one of the two standards. Additional ciruitry is needed to connect to a microprocessor employing the other standard. One solution to this restriction of devices is a Motorola "Motel" interface used on the Motorola MC146818 part. The "Motel" interface allows either microprocessor type to be connected to the part. However, this interface requires a 3-wire interconnection, including a separate timing signal.
Thus the prior art has employed discrete and/or custom integrated circuitry which lacks the flexibility to meet changing needs, because the timing signal is not always available.